In recent decades, terahertz wave has become an important research topic in the physics because of its wide application prospect. The terahertz radiation is an electromagnetic wave with a frequency ranging from 0.1 to 10 THz. Such wave, with abundant information, high spatial-temporal coherence, low photon energy, etc., is located between the microwave and the infrared, and is of great values in astronomy, biology, computer science, communications and other applications. At present, main application researches include terahertz time-domain spectroscopy, terahertz imaging, security check, terahertz radar, astronomy and communications.
The emergence and development of the terahertz spectroscopy provides a new breakthrough for the biomedical research. Researches in recent years have indicated that for most biological molecules, the rotational energy level, vibrational energy level and weak intermolecular interaction energy level are located in the terahertz waveband. Weak intermolecular interaction involves hydrogen bonds existing in many molecules, and the rotational and vibrational motions of the molecules also fall exactly in the terahertz waveband. Therefore, the technique of terahertz spectroscopy can be used to study the spectral and kinetic properties of biomolecules.
Currently, in the biological detection using terahertz spectroscopy, methods for preparing biological samples generally include paraffin-embedding, tableting with PE powder, sandwiching with Teflon and so on.
However, these methods have their disadvantages. For example, for the paraffin-embedding method, the samples may have a high moisture content, which will affect the transmission of terahertz signals, and then reduce the amplitude of the detected terahertz signal significantly; for the method of tableting with PE powder, when there are relatively fewer biological samples, the area where terahertz waves act upon the samples is very small and then it will be very difficult to find characteristic peaks in spectrum; the method of sandwiching with Teflon is only applicable to the case where the sample size is sufficient large and the moisture content is low.
Therefore, there is a need to solve the problems existing in the biological sample detection, namely, the small number of samples and the moisture in the samples, which leads to the absorption spectral signals too weak or even mixed with the background noise and thus difficult to distinguish. So far, no effective methods have been proposed to solve the above problems.